This invention relates to a valve timing system, and more particularly, to a valve timing system which dynamically and selectively suppresses knocking within the various cylinders of an internal combustion engine.
Valve timing systems, arrangements and assemblies are used in internal combustion engines in order to alter the timing of the opening and closing of the engine""s intake and/or exhaust valves. Prior valve timing systems typically include one or more camshafts and one or more cam timing assemblies which selectively advance and/or delay the rotation of the one or more camshafts, thereby controlling the actuation of the intake and exhaust valves.
These prior systems and the valve timing profiles used by these systems suffer from several drawbacks. Particularly, due to their inherent physical limitations, these prior cam-driven systems are ineffective to adjust or control valve xe2x80x9coverlapxe2x80x9d (i.e., situations in which both the intake and exhaust valves are open) during vehicle operation. In order to generate maximum power at high speeds, a relatively high degree of valve overlap is required. However, at low speeds (e.g., at idling conditions) a high degree of valve overlap undesirably causes high emissions and increases the susceptibility to engine knock. Due to the inability of these prior systems to efficiently and dynamically adjust the timing of the valves during different vehicle operating modes, the valve timing profiles or strategies used within these prior systems typically compromise between power output at high engine speeds and proper idling at low engine speeds. As a result, these prior systems generally cannot maximize power and fuel efficiency and minimize emissions at both high and low engine operating speeds. Moreover, these cam-driven systems lack the ability to independently control individual valves during the operation of the vehicle. Hence, these systems cannot dynamically suppress or control harmful conditions such as knocking within the individual cylinders of the engine during operation of the vehicle.
Efforts have been made to increase the efficiency of vehicle engines and reduce emissions by eliminating the camshafts and operating the intake and exhaust valves by use of selectively controllable electromagnetic actuators. These types of systems eliminate many problems related to the physical characteristics of cam-driven systems and offer additional precision in valve timing. However, these prior systems are typically implemented for the purpose of improving fuel economy and emissions and do not address knock control. Thus, these systems suffer from many of the same previously delineated drawbacks associated with cam-driven systems. For example and without limitation, the same valve timing is commanded to each cylinder regardless of the propensity of that cylinder to knock. Consequently, these systems are unable to be selectively and dynamically altered to suppress or control cylinder knocking during the operation of the vehicle. Such systems rely on retarding spark timing in order to suppress knock, coupled with enriching the air-fuel mixture in severe knocking conditions. Both of these measures result in undesirably increasing emissions and fuel consumption. With the present invention, valve timing is altered to respond to knock by reducing the amount of mixture drawn into the knocking cylinder, and thus air-fuel ratios and spark timing are maintained at optimum levels for fuel economy and emissions.
There is therefore a need for a new and improved valve timing system for use with a camless engine which dynamically suppresses knocking within the individual cylinders of the engine without adversely effecting fuel economy and emissions.
It is a first object of the invention to provide a valve timing system which overcomes at least some of the previously delineated drawbacks of prior valve timing systems, assemblies and methodologies.
It is a second object of the invention to provide a valve timing system for use in combination with a camless internal combustion engine which dynamically suppresses knocking within the various cylinders of the engine.
It is a third object of the invention to provide a valve timing system for use within an engine which utilizes several electromagnetic valve actuating assemblies which are dynamically and independently controlled to suppress cylinder knocking while the engine is operating without having to alter the air-fuel ratio and spark timing from optimum levels for fuel economy and emissions.
According to a first aspect of the present invention, a valve timing system is provided for use within a camless engine of the type including a cylinder having at least one valve. The valve timing system includes at least one actuator which selectively actuates the at least one valve; a sensor which is effective to detect knocking within the cylinder, and to generate a first signal in response to the detection; and a controller which is communicatively coupled to the at least one actuator and to the sensor, the controller being effective to receive the signal and to selectively communicate a second signal to the at least one actuator, the second signal having a value based upon the first signal and being effective to cause the at least one actuator to alter the actuation of the at least one valve while the engine is operating, thereby dynamically suppressing the knocking within the cylinder.
These and other features, aspects, and advantages of the invention will become apparent by reading the following specification and by reference to the following drawings.